Cells of the mammalian uterus exhibit growth in response to estrogens and to decidual stimuli when properly sensitized. I have found that the uterus of the unsensitized, ovariectomized rat will respond to transcervical, intrauterine injection of saline (a decidual stimulus) in a manner similar to the estradiol-induced initiation phase of uterine growth, with respect to increase in RNA synthesis and ornithine decarboxylase activity. This initiation of growth caused by intrauterine injection, however, more closely resembles the response of the uterus to estriol, in that growth is not maintained as it is with estradiol. The main objective of the proposed research is to further characterize this response of the uterus to intrauterine injection and compare it with the growth responses initiated by estrogens and decidual stimuli, with respect to various biochemical, morphological, and developmental parameters. Is is my hypothesis that certain initial aspects of all three growth responses may involve a common mechanism. The uterus of the ovarectomized rabbit will also be tested for its response to intrauterine injection. Similar studies will be carried out using the chick oviduct, wherein trauma has been shown to cause the induction of avidin, a response normally elicited by progesterone.